The present invention relates generally to ferrules used in welding studs to a work surface. In particular, it relates to a dispenser for placing the individual ferrules on the work surface, and to packaging and loading ferrules for use with the dispenser.
During structural construction, metal studs are commonly used to improve shear strength in concrete slabs and to provide mounting structure for components of a structural framework. The studs can be connected directly to a bare beam of a structure or can be connected through metal decking to an underlying beam of a structure. An arc welding process, such as drawn arc welding, is often used to make these connections. When using the drawn arc process, ceramic ferrules are positioned around a base of the stud. The ferrules concentrate weld heat between the stud and the work surface and contain the molten pool of melted metal around the base of the stud. This improves quality of the weld and facilitates formation of a strong weld filet.
Ferrules are usually ordered based on the number of studs to weld. But they are usually packaged based on weight. This can lead to inaccurate orders because a moisture content and a density of each ferrule may vary. Two boxes of ferrules with similar weights may contain a significantly different numbers of ferrules. The ferrules are also randomly packaged in boxes prior to shipping. This can damage a substantial number of the ferrules and can possibly leave only a fraction of the received ferrules usable. Accordingly, accurately ordering a desired number of ferrules for a stud welding project can be difficult.
In response to these drawbacks, ferrule manufactures may use a ferrule retainer to ship the ferrules. Examples are shown in U.S. Pat. Nos. 4,600,118 and 5,704,515, the disclosures of which are hereby incorporated by reference. These retainers are capable of holding a set number of ferrules in a uniform arrangement and can reduce potential damage to the ferrules that may occur during shipping. The retainers usually include a restraining feature at the ends for holding the ferrules in place. But having two restraining features can be somewhat burdensome. They require an additional step in making and loading the retainers because at least one of the restraining features must be subsequently added after the ferrules are loaded. They also require an additional step to access the ferrules at the work site because at least one of the restraining features must be removed. Accordingly, there is a need for a simple and efficient way to ship ferrules to a work site.
At the work site, it is known to have workers place the ferrules at predetermined locations along the work surface by hand, repeatedly bending over to do so. At the same time, the worker properly orients the ferrule. As the ferrules are placed, the worker may drag the box of ferrules alongside in order to maintain a constant supply. This, however, is extremely time consuming and physically demanding. So as an alternative, the worker may pre-load ferrules into a bolt bag. But this is also inefficient as the worker must constantly re-fill the bag. In addition, the pre-loaded ferrules are subject to damage and still require repeated bending to place.
In response to these inefficiencies, a ferrule applicator may be used to place the ferrules on the work surface and thereby reduce the physical stress of repeated bending. Examples of applicators are shown in U.S. Pat. Nos. 4,600,118, 5,704,515, and 6,112,944. Ferrule applicators of the prior art are generally capable of holding multiple ferrules in a uniform arrangement for repetitious placing on the work surface. In a common prior art applicator, ball bearings are located around one end of the applicator for selectively holding the ferrules or releasing them onto the work surface. In some of these applicators, the ferrules are retained inside the applicator. A spring loaded tubular plunger slides over an outer surface of the applicator and biases the ball bearings to either engage the ferrules and retain them inside the applicator or release the ferrules and allow them to fall to the work surface. In other applicators, the ferrules are retained on an outer surface of the applicator. A spring loaded plunger slides longitudinally inside the applicator and again biases ball bearings to selectively retain or release the ferrules.
But these prior art applicators have drawbacks. For example, the ball bearings may stick or wedge in either a hold position or a release position, resulting in inconsistent operation. In addition, the ball bearings may inadvertently engage a side surface of a ferrule as it is released. This can possibly jam the ferrule on (or in) the applicator and can potentially damage the ferrule so that it is unusable. Moreover, the ball bearings may only move partially into and out of the applicator. As a result, an irregular ferrule with a slightly larger than average diameter may not be effectively retained, and an irregular ferrule with a slightly smaller than average diameter may not fully pass over the bearings.
Accordingly, there is a need for a ferrule retainer that loads quickly and easily, and that reliably retains ferrules during shipping or storing. In addition, there is a need for a ferrule retainer that allows easy access to the retained ferrules at a work site. There is a further need for a ferrule applicator that can reliably place ferrules onto a work surface without jamming and without damaging the ferrules, and that can consistently operate time after time.